The present invention relates to a drive mechanism, and more particularly to a drive mechanism having two output shafts, each of which is sequentially selected to receive power from a single input shaft.
There are many situations in which a rotary drive must be applied to one task and then, after a predetermined number of rotations, shifted to another related task. In aircraft equipped with multiple wing flaps, for example, the main flap is adjusted first, followed by a smaller flap on the trailing edge. Conventionally, this requires two power actuators operated in sequence and controlled by electric circuitry and accompanying position sensors.
Other aircraft are provided with pivotable wings so that they can be moved from a folded or stored position to a conventional in-flight position. After the wings have unfolded, they must be secured by a latch pin. Conventionally, the wing is moved by a motor, but must be latched by a separately powered operation. The same steps are performed in the reverse sequence to return the wings to their folded position.
In repetitive aircraft operations of the above type, mechanical limiting devices have been employed which limit the number of rotations of a shaft used, for example, to fold the wings of the aircraft. One such limiting device utilizes two or more notched concentric cams that are rotated at different speeds. After a predetermined number of revolutions, the notches become aligned and a pawl that engages all of the cams simultaneously drops into the notches, thereby arresting the power supply shaft. The cams are driven by concentric cam-drive gears that are of equal diameter but have different numbers of teeth. One of these gears is a master gear and the others are slave gears, the slave gears being driven by the master gear through an idler gear.
While these previously known limiting mechanisms are capable of arresting the rotation of a shaft at the proper time, they apply only to one separately powered task. Accordingly, they have no true sequencing function.
There are many such repetitive sequential operations that could be performed advantageously by a single mechanical drive mechanism, if such a mechanism could be devised that is simple and compact, but nevertheless provides the desired outputs in the proper predetermined sequence with the necessary precision.